User Tutorial:Introduction to the Mu Rhythm - Revision history

Mellinger at 09:50, 5 June 2023

2023-06-05T09:50:58Z

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	[[Image:MuRhythmModulation.PNG\|471px]]		[[Image:MuRhythmModulation.PNG\|471px]]

	The figure displays examples of modulated mu rhythm signals (modified from [~~http~~://{{SERVERNAME}}/downloads/doc/paper.pdf]).		The figure displays examples of modulated mu rhythm signals (modified from [https://{{SERVERNAME}}/downloads/doc/paper.pdf]).
	*A,B: Topographical distribution on the scalp of the difference (measured as <math>r^2</math> (the proportion of the single-trial variance that is due to the task)), calculated for actual (A) and imagined (B) right-hand movements vs. rest for a 3 Hz band centered at 12 Hz.		*A,B: Topographical distribution on the scalp of the difference (measured as <math>r^2</math> (the proportion of the single-trial variance that is due to the task)), calculated for actual (A) and imagined (B) right-hand movements vs. rest for a 3 Hz band centered at 12 Hz.
	*C: Example voltage spectra for a different subject and a location over left sensorimotor cortex (i.e., C3) for comparing rest (dashed line) and imagery (solid line).		*C: Example voltage spectra for a different subject and a location over left sensorimotor cortex (i.e., C3) for comparing rest (dashed line) and imagery (solid line).

Mellinger at 15:19, 20 December 2008

2008-12-20T15:19:23Z

← Older revision		Revision as of 15:19, 20 December 2008
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	In human EEG, primary sensory or motor cortical areas typically exhibit rhythmic		In human EEG, primary sensory or motor cortical areas typically exhibit rhythmic
	activity at a frequency of approximately 8-12 Hz when they are not processing sensory information		activity at a frequency of approximately 8-12 Hz when they are not processing sensory information
	or producing motor output. This activity is called mu rhythm in is thought to		or producing motor output. This activity is called mu rhythm, and is thought to
	be produced by interactions between the thalamus and the cortex. Computer-based		be produced by interactions between the thalamus and the cortex. Computer-based
	analyses have demonstrated that mu rhythm activity consists of a variety of different		analyses have demonstrated that mu rhythm activity consists of a variety of different

Gschalk at 20:06, 21 October 2008

2008-10-21T20:06:26Z

← Older revision		Revision as of 20:06, 21 October 2008
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	In ~~awake people~~, primary sensory or motor cortical areas typically ~~display~~ rhythmic ~~EEG~~ activity ~~with~~ a ~~base~~ frequency of 8-12 Hz when they are not ~~engaged in~~ processing sensory ~~input~~ or producing		In human EEG, primary sensory or motor cortical areas typically exhibit rhythmic
	motor output. This ~~idling~~ activity, called mu rhythm		activity at a frequency of approximately 8-12 Hz when they are not processing sensory information
	~~when recorded over sensorimotor cortex and visual alpha rhythm when recorded~~		or producing motor output. This activity is called mu rhythm in is thought to
	~~over visual cortex,~~ is thought to be produced by ~~thalamocortical circuits. Unlike~~		be produced by interactions between the thalamus and the cortex. Computer-based
	the ~~visual alpha rhythm, which is obvious in a large majority of normal people,~~		analyses have demonstrated that mu rhythm activity consists of a variety of different
	the ~~mu rhythm was until quite recently thought to occur in only a minority of~~		8-12 Hz rhythms that are distinguished
	~~people~~. ~~However, computer~~-based ~~analyses have shown that the mu rhythm is~~
	~~present in a large majority of adults. Such~~ analyses have ~~also shown~~ that
	mu rhythm activity ~~comprises~~ a variety of different 8-12 Hz rhythms, distinguished
	from each other by precise location, precise frequency, and/or typical relationship		from each other by precise location, precise frequency, and/or typical relationship
	to concurrent sensory input or motor output.		to concurrent sensory input or motor output.

Mellinger: /* Carrier Demodulation */

2008-08-23T06:54:09Z

Carrier Demodulation

← Older revision		Revision as of 06:54, 23 August 2008
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	===Carrier Demodulation===		===Carrier Demodulation===
	After extracting the carrier signal, its amplitude time series (envelope) must be computed to obtain the original signal impressed onto the carrier. In a simple AM receiver, this is done using a rectifier diode in conjunction with a low pass circuit. If a BCI employs bandpass filtering for frequency selection, calculating the mean amplitude over a short interval usually performs the equivalent function.		After extracting the carrier signal by spatial and temporal filtering, its amplitude time series (envelope) must be computed to obtain the original signal impressed onto the carrier. In a simple AM receiver, this is done using a rectifier diode in conjunction with a low pass circuit. If a BCI employs bandpass filtering for frequency selection, calculating the mean amplitude over a short interval usually performs the equivalent function.

	For BCIs using spectral estimation methods, demodulation is often implemented inside the spectral estimation step, with its output being a distribution of absolute amplitude values.		For BCIs using spectral estimation methods, demodulation is often implemented inside the spectral estimation step, with its output being a distribution of absolute amplitude values.

Mellinger: /* Frequency Selection */

2008-08-23T06:52:02Z

Frequency Selection

← Older revision		Revision as of 06:52, 23 August 2008
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	===Frequency Selection===		===Frequency Selection===
	All mu rhythm BCIs employ some type of frequency selection, favoring signals in a narrow band around a single, or multiple, ~~peaks~~ of the mu rhythm's spectrum. There is a number of possibilities to implement frequency selection; most common are		All mu rhythm BCIs employ some type of frequency selection, favoring signals in a narrow band around a single peak, or multiple peaks, of the mu rhythm's spectrum. There is a number of possibilities to implement frequency selection; most common are
	*IIR bandpass filtering,		*IIR bandpass filtering,
	*windowed spectral estimation methods such as		*windowed spectral estimation methods such as

Mellinger: /* Spatial Selection */

2008-08-23T06:51:10Z

Spatial Selection

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	Consequently, its signal processing chain is analogous to that of an AM receiver.		Consequently, its signal processing chain is analogous to that of an AM receiver.
	===Spatial Selection===		===Spatial Selection===
	Using a linear combination of simultaneous input samples, the [[User Reference:SpatialFilter\|spatial filtering]] step favors signals originating from hand/feet areas. In the AM receiver analogy, this step corresponds to a directional antenna that favors radio signals originating from the spatial direction corresponding to a desired broadcasting station's position over signals from undesired broadcasting stations, or noise.		Using a linear combination of simultaneous input samples, the [[User Reference:SpatialFilter\|spatial filtering]] step favors signals originating from hand/feet areas over signals that originate from other areas. In the AM receiver analogy, this step corresponds to a directional antenna that favors radio signals originating from the spatial direction corresponding to a desired broadcasting station's position over signals from undesired broadcasting stations, or spatially inhomogeneous noise.

	===Frequency Selection===		===Frequency Selection===

Mellinger: /* Location */

2008-08-23T06:45:14Z

Location

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	[[Image:SensorimotorAreas.PNG\|376px]]		[[Image:SensorimotorAreas.PNG\|376px]]

	In its center, the figure displays a human brain viewed from above, with the frontal direction pointing downward. At the top of the figure, a vertical cross-section of the brain is depicted, taken along motor resp. sensory cortex. On the left side, the ''motor'' cortex is displayed in red, associated with a "motor homunculus" illustrating which regions are allocated for controlling the respective limb and facial muscles. Similarly, on the right, ''sensory'' areas are illustrated by a "sensory homunculus".		In its center, the figure displays a human brain viewed from above, with the frontal direction pointing downward. At the top of the figure, a vertical cross-section of the brain is depicted, taken along motor resp. sensory cortex. On the left side, the ''motor'' cortex is displayed in red, associated with a "motor homunculus" illustrating which regions are allocated for controlling the respective limb and facial muscles. Similarly, on the right, ''sensory'' areas are illustrated by a "sensory homunculus" indicating which regions are allocated for processing sensory information from the respective parts of the body.
			The ''separation'' between motor and sensory cortices is a [[User_Tutorial:EEG_Measurement_Setup#Identifying_Brain_Areas\|major landmark of brain anatomy]], and is called the '''central sulcus''' or '''rolandic fissure'''.

	The mu rhythm originates from the hand area of the motor cortex. Also, there is a similar rhythm originating from the motor cortex' foot area, which is located between hemispheres.		The mu rhythm originates from the hand area of the motor cortex. Also, there is a similar rhythm originating from the motor cortex' foot area, which is located between hemispheres.

	The separation between motor and sensory cortices is a [[User_Tutorial:EEG_Measurement_Setup#Identifying_Brain_Areas\|major landmark of brain anatomy]], and is called the '''central sulcus''' or '''rolandic fissure'''.

	====Orientation====		====Orientation====

Mellinger: /* Scalp Potential */

2008-08-23T06:41:41Z

Scalp Potential

← Older revision		Revision as of 06:41, 23 August 2008
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	The figure displays typical mu rhythm scalp potential distributions (adapted from B Blankertz, R Tomioka, S Lemm, M Kawanabe, and KR Müller: Optimizing spatial filters for robust EEG single-trial analysis. IEEE Signal Proc. Magazine, 25(1):41-56, January 2008, reproduced with permission of the authors).		The figure displays typical mu rhythm scalp potential distributions (adapted from B Blankertz, R Tomioka, S Lemm, M Kawanabe, and KR Müller: Optimizing spatial filters for robust EEG single-trial analysis. IEEE Signal Proc. Magazine, 25(1):41-56, January 2008, reproduced with permission of the authors).

	The distribution on the left illustrates the topography associated with a radially oriented source dipole (1) located on the right hemispheric motor gyrus.		The distribution on the left illustrates the topography associated with a radially oriented source dipole (1) located on the right hemispheric motor '''gyrus'''.
	The distribution to the right is due to a tangentially oriented source dipole located in the central sulcus (2).		The distribution to the right is due to a tangentially oriented source dipole located in the central '''sulcus''' (2).

	For source locations intermediate between (1) and (2), dipole orientation will be a linear combination of radial and tangential orientations. On the scalp, this results in a linear combination of associated scalp potential distributions (1) and (2).		For source locations intermediate between (1) and (2), dipole orientation will be a linear combination of radial and tangential orientations. On the scalp, this results in a linear combination of associated scalp potential distributions (1) and (2).

Mellinger: /* Orientation */

2008-08-23T06:40:26Z

Orientation

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	[[Image:GyrusSulcus.PNG\|400px]]		[[Image:GyrusSulcus.PNG\|400px]]

	The mu rhythm's geometric source character is that of a dipole, with the dipole moment pointing perpendicular to the folded cortical surface. Thus, the orientation of the dipole moment is determined by the dipole's location: With regard to the scalp, a location in a ''gyrus'' will have a radial orientiation (1), while a location in a ''sulcus'' will result in a dipole orientation that is tangential to the scalp (2). In the latter case, the dipole moment will be perpendicular to the central sulcus as well as tangential to the scalp.		The mu rhythm's geometric source character is that of a dipole, with the dipole moment pointing perpendicular to the folded cortical surface. Thus, the orientation of the dipole moment is determined by the dipole's location: With regard to the scalp, a location in a ''gyrus'' will have a radial orientiation (1), while a location in a ''sulcus'' will result in a dipole orientation that is tangential to the scalp (2). In the latter case, the dipole moment will be perpendicular to the '''central sulcus''' as well as tangential to the scalp.

	====Scalp Potential====		====Scalp Potential====

Mellinger: /* Location */

2008-08-23T06:40:04Z

Location

← Older revision		Revision as of 06:40, 23 August 2008
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	In its center, the figure displays a human brain viewed from above, with the frontal direction pointing downward. At the top of the figure, a vertical cross-section of the brain is depicted, taken along motor resp. sensory cortex. On the left side, the ''motor'' cortex is displayed in red, associated with a "motor homunculus" illustrating which regions are allocated for controlling the respective limb and facial muscles. Similarly, on the right, ''sensory'' areas are illustrated by a "sensory homunculus".		In its center, the figure displays a human brain viewed from above, with the frontal direction pointing downward. At the top of the figure, a vertical cross-section of the brain is depicted, taken along motor resp. sensory cortex. On the left side, the ''motor'' cortex is displayed in red, associated with a "motor homunculus" illustrating which regions are allocated for controlling the respective limb and facial muscles. Similarly, on the right, ''sensory'' areas are illustrated by a "sensory homunculus".
	The mu rhythm originates from the hand area of the motor cortex. Also, there is a similar rhythm originating from the motor cortex' foot area, which is located between hemispheres.		The mu rhythm originates from the hand area of the motor cortex. Also, there is a similar rhythm originating from the motor cortex' foot area, which is located between hemispheres.

			The separation between motor and sensory cortices is a [[User_Tutorial:EEG_Measurement_Setup#Identifying_Brain_Areas\|major landmark of brain anatomy]], and is called the '''central sulcus''' or '''rolandic fissure'''.

	====Orientation====		====Orientation====